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2016-04-05Add parallel query support functions for assorted aggregates.Robert Haas
This lets us use parallel aggregate for a variety of useful cases that didn't work before, like sum(int8), sum(numeric), several versions of avg(), and various other functions. Add some regression tests, as well, testing the general sanity of these and future catalog entries. David Rowley, reviewed by Tomas Vondra, with a few further changes by me.
2016-04-04Disallow newlines in parameter values to be set in ALTER SYSTEM.Tom Lane
As noted by Julian Schauder in bug #14063, the configuration-file parser doesn't support embedded newlines in string literals. While there might someday be a good reason to remove that restriction, there doesn't seem to be one right now. However, ALTER SYSTEM SET could accept strings containing newlines, since many of the variable-specific value-checking routines would just see a newline as whitespace. This led to writing a postgresql.auto.conf file that was broken and had to be removed manually. Pending a reason to work harder, just throw an error if someone tries this. In passing, fix several places in the ALTER SYSTEM logic that failed to provide an errcode() for an ereport(), and thus would falsely log the failure as an internal XX000 error. Back-patch to 9.4 where ALTER SYSTEM was introduced.
2016-04-04Introduce a LOG_SERVER_ONLY ereport level, which is never sent to client.Tom Lane
This elevel is useful for logging audit messages and similar information that should not be passed to the client. It's equivalent to LOG in terms of decisions about logging priority in the postmaster log, but messages with this elevel will never be sent to the client. In the current implementation, it's just an alias for the longstanding COMMERROR elevel (or more accurately, we've made COMMERROR an alias for this). At some point it might be interesting to allow a LOG_ONLY flag to be attached to any elevel, but that would be considerably more complicated, and it's not clear there's enough use-cases to justify the extra work. For now, let's just take the easy 90% solution. David Steele, reviewed by Fabien Coelho, Petr Jelínek, and myself
2016-04-04Improve estimate of distinct values in estimate_num_groups().Dean Rasheed
When adjusting the estimate for the number of distinct values from a rel in a grouped query to take into account the selectivity of the rel's restrictions, use a formula that is less likely to produce under-estimates. The old formula simply multiplied the number of distinct values in the rel by the restriction selectivity, which would be correct if the restrictions were fully correlated with the grouping expressions, but can produce significant under-estimates in cases where they are not well correlated. The new formula is based on the random selection probability, and so assumes that the restrictions are not correlated with the grouping expressions. This is guaranteed to produce larger estimates, and of course risks over-estimating in cases where the restrictions are correlated, but that has less severe consequences than under-estimating, which might lead to a HashAgg that consumes an excessive amount of memory. This could possibly be improved upon in the future by identifying correlated restrictions and using a hybrid of the old and new formulae. Author: Tomas Vondra, with some hacking be me Reviewed-by: Mark Dilger, Alexander Korotkov, Dean Rasheed and Tom Lane Discussion: http://www.postgresql.org/message-id/flat/56CD0381.5060502@2ndquadrant.com
2016-04-01Copyedit comments and documentation.Noah Misch
2016-03-30Improve portability of I/O behavior for the geometric types.Tom Lane
Formerly, the geometric I/O routines such as box_in and point_out relied directly on strtod() and sprintf() for conversion of the float8 component values of their data types. However, the behavior of those functions is pretty platform-dependent, especially for edge-case values such as infinities and NaNs. This was exposed by commit acdf2a8b372aec1d, which added test cases involving boxes with infinity endpoints, and immediately failed on Windows and AIX buildfarm members. We solved these problems years ago in the main float8in and float8out functions, so let's fix it by making the geometric types use that code instead of depending directly on the platform-supplied functions. To do this, refactor the float8in code so that it can be used to parse just part of a string, and as a convenience make the guts of float8out usable without going through DirectFunctionCall. While at it, get rid of geo_ops.c's fairly shaky assumptions about the maximum output string length for a double, by having it build results in StringInfo buffers instead of fixed-length strings. In passing, convert all the "invalid input syntax for type foo" messages in this area of the code into "invalid input syntax for type %s" to reduce the number of distinct translatable strings, per recent discussion. We would have needed a fair number of the latter anyway for code-sharing reasons, so we might as well just go whole hog. Note: this patch is by no means intended to guarantee that the geometric types uniformly behave sanely for infinity or NaN component values. But any bugs we have in that line were there all along, they were just harder to reach in a platform-independent way.
2016-03-30Suppress uninitialized-variable warnings.Tom Lane
My compiler doesn't like the lack of initialization of "flag", and I think it's right: if there were zero keys we'd have an undefined result. The AND of zero items is TRUE, so initialize to TRUE.
2016-03-30Introduce SP-GiST operator class over box.Teodor Sigaev
Patch implements quad-tree over boxes, naive approach of 2D quad tree will not work for any non-point objects because splitting space on node is not efficient. The idea of pathc is treating 2D boxes as 4D points, so, object will not overlap (in 4D space). The performance tests reveal that this technique especially beneficial with too much overlapping objects, so called "spaghetti data". Author: Alexander Lebedev with editorization by Emre Hasegeli and me
2016-03-30Use traversalValue in SP-GiST range opclass.Teodor Sigaev
Author: Alexander Lebedev
2016-03-29Add new replication mode synchronous_commit = 'remote_apply'.Robert Haas
In this mode, the master waits for the transaction to be applied on the remote side, not just written to disk. That means that you can count on a transaction started on the standby to see all commits previously acknowledged by the master. To make this work, the standby sends a reply after replaying each commit record generated with synchronous_commit >= 'remote_apply'. This introduces a small inefficiency: the extra replies will be sent even by standbys that aren't the current synchronous standby. But previously-existing synchronous_commit levels make no attempt at all to optimize which replies are sent based on what the primary cares about, so this is no worse, and at least avoids any extra replies for people not using the feature at all. Thomas Munro, reviewed by Michael Paquier and by me. Some additional tweaks by me.
2016-03-29Fix interval_mul() to not produce insane results.Tom Lane
interval_mul() attempts to prevent its calculations from producing silly results, but it forgot that zero times infinity yields NaN in IEEE arithmetic. Hence, a case like '1 second'::interval * 'infinity'::float8 produced a NaN for the months product, which didn't trigger the range check, resulting in bogus and possibly platform-dependent output. This isn't terribly obvious to the naked eye because if you try that exact case, you get "interval out of range" which is what you expect --- but if you look closer, the error is coming from interval_out not interval_mul. interval_mul has allowed a bogus value into the system. Fix by adding isnan tests. Noted while testing Vitaly Burovoy's fix for infinity input to to_timestamp(). Given the lack of field complaints, I doubt this is worth a back-patch.
2016-03-29Allow to_timestamp(float8) to convert float infinity to timestamp infinity.Tom Lane
With the original SQL-function implementation, such cases failed because we don't support infinite intervals. Converting the function to C lets us bypass the interval representation, which should be a bit faster as well as more flexible. Vitaly Burovoy, reviewed by Anastasia Lubennikova
2016-03-28Document errhidecontext() where it ought to be documented.Tom Lane
Seems to have been missed when this function was added. Noted while looking at David Steele's proposal to add another similar function.
2016-03-28Reset plan->row_security_env and planUserIdStephen Frost
In the plancache, we check if the environment we planned the query under has changed in a way which requires us to re-plan, such as when the user for whom the plan was prepared changes and RLS is being used (and, therefore, there may be different policies to apply). Unfortunately, while those values were set and checked, they were not being reset when the query was re-planned and therefore, in cases where we change role, re-plan, and then change role again, we weren't re-planning again. This leads to potentially incorrect policies being applied in cases where role-specific policies are used and a given query is planned under one role and then executed under other roles, which could happen under security definer functions or when a common user and query is planned initially and then re-used across multiple SET ROLEs. Further, extensions which made use of CopyCachedPlan() may suffer from similar issues as the RLS-related fields were not properly copied as part of the plan and therefore RevalidateCachedQuery() would copy in the current settings without invalidating the query. Fix by using the same approach used for 'search_path', where we set the correct values in CompleteCachedPlan(), check them early on in RevalidateCachedQuery() and then properly reset them if re-planning. Also, copy through the values during CopyCachedPlan(). Pointed out by Ashutosh Bapat. Reviewed by Michael Paquier. Back-patch to 9.5 where RLS was introduced. Security: CVE-2016-2193
2016-03-28Code and docs review for commit 3187d6de0e5a9e805b27c48437897e8c39071d45.Tom Lane
Fix up check for high-bit-set characters, which provoked "comparison is always true due to limited range of data type" warnings on some compilers, and was unlike the way we do it elsewhere anyway. Fix omission of "$" from the set of valid identifier continuation characters. Get rid of sanitize_text(), which was utterly inconsistent with any other error report anywhere in the system, and wasn't even well designed on its own terms (double-quoting the result string without escaping contained double quotes doesn't seem very well thought out). Fix up error messages, which didn't follow the message style guidelines very well, and were overly specific in situations where the actual mistake might not be what they said. Improve documentation. (I started out just intending to fix the compiler warning, but the more I looked at the patch the less I liked it.)
2016-03-27Guard against zero vardata.rel->tuples in estimate_hash_bucketsize().Tom Lane
If the referenced rel was proven empty, we'd compute 0/0 here, which results in the function returning NaN. That's a bit more serious than the other zero-divide case. Still, it only seems to be possible in HEAD, so no back-patch. Per report from Piotr Stefaniak. I looked through the rest of selfuncs.c and found no other likely trouble spots.
2016-03-27Clamp adjusted ndistinct to positive integer in estimate_hash_bucketsize().Tom Lane
This avoids a possible divide-by-zero in the following calculation, and rounding the number to an integer seems like saner behavior anyway. Assuming IEEE math, the division would yield +Infinity which would get replaced by 1.0 at the bottom of the function, so nothing really interesting would ensue; but avoiding divide-by-zero seems like a good idea on general principles. Per report from Piotr Stefaniak. No back-patch since this seems mostly cosmetic.
2016-03-25Improve PL/Tcl errorCode facility by providing decoded name for SQLSTATE.Tom Lane
We don't really want to encourage people to write numeric SQLSTATEs in programs; that's unreadable and error-prone. Copy plpgsql's infrastructure for converting between SQLSTATEs and exception names shown in Appendix A, and modify examples in tests and documentation to do it that way.
2016-03-24Use correct GetDatum function.Robert Haas
Oops.
2016-03-23Support CREATE ACCESS METHODAlvaro Herrera
This enables external code to create access methods. This is useful so that extensions can add their own access methods which can be formally tracked for dependencies, so that DROP operates correctly. Also, having explicit support makes pg_dump work correctly. Currently only index AMs are supported, but we expect different types to be added in the future. Authors: Alexander Korotkov, Petr Jelínek Reviewed-By: Teodor Sigaev, Petr Jelínek, Jim Nasby Commitfest-URL: https://commitfest.postgresql.org/9/353/ Discussion: https://www.postgresql.org/message-id/CAPpHfdsXwZmojm6Dx+TJnpYk27kT4o7Ri6X_4OSWcByu1Rm+VA@mail.gmail.com
2016-03-23Move keywords.c/kwlookup.c into src/common/.Tom Lane
Now that we have src/common/ for code shared between frontend and backend, we can get rid of (most of) the klugy ways that the keyword table and keyword lookup code were formerly shared between different uses. This is a first step towards a more general plan of getting rid of special-purpose kluges for sharing code in src/bin/. I chose to merge kwlookup.c back into keywords.c, as it once was, and always has been so far as keywords.h is concerned. We could have kept them separate, but there is noplace that uses ScanKeywordLookup without also wanting access to the backend's keyword list, so there seems little point. ecpg is still a bit weird, but at least now the trickiness is documented. I think that the MSVC build script should require no adjustments beyond what's done here ... but we'll soon find out.
2016-03-23Disable abbreviated keys for string-sorting in non-C locales.Robert Haas
Unfortunately, every version of glibc thus far tested has bugs whereby strcoll() ordering does not match strxfrm() ordering as required by the standard. This can result in, for example, corrupted indexes. Disabling abbreviated keys in these cases slows down non-C-collation string sorting considerably, but there seems to be no practical alternative. Users who are confident that their libc implementations are solid in this regard can re-enable the optimization by compiling with TRUST_STRXFRM. Users who have built indexes using PostgreSQL 9.5 or PostgreSQL 9.5.1 should REINDEX if there is a possibility that they may have been affected by this problem. Report by Marc-Olaf Jaschke. Investigation mostly by Tom Lane, with help from Peter Geoghegan, Noah Misch, Stephen Frost, and me. Patch by me, reviewed by Peter Geoghegan and Tom Lane.
2016-03-23Partition the freelist for shared dynahash tables.Robert Haas
Without this, contention on the freelist can become a pretty serious problem on large servers. Aleksander Alekseev, reviewed by Anastasia Lubennikova, Dilip Kumar, and me.
2016-03-23Code review for error reports in jsonb_set().Tom Lane
User-facing (even tested by regression tests) error conditions were thrown with elog(), hence had wrong SQLSTATE and were untranslatable. And the error message texts weren't up to project style, either.
2016-03-23Fix unsafe use of strtol() on a non-null-terminated Text datum.Tom Lane
jsonb_set() could produce wrong answers or incorrect error reports, or in the worst case even crash, when trying to convert a path-array element into an integer for use as an array subscript. Per report from Vitaly Burovoy. Back-patch to 9.5 where the faulty code was introduced (in commit c6947010ceb42143). Michael Paquier
2016-03-21Make max_parallel_degree PGC_USERSET.Robert Haas
It was intended to be this way all along, just like other planner GUCs such as work_mem. But I goofed.
2016-03-21Introduce WaitEventSet API.Andres Freund
Commit ac1d794 ("Make idle backends exit if the postmaster dies.") introduced a regression on, at least, large linux systems. Constantly adding the same postmaster_alive_fds to the OSs internal datastructures for implementing poll/select can cause significant contention; leading to a performance regression of nearly 3x in one example. This can be avoided by using e.g. linux' epoll, which avoids having to add/remove file descriptors to the wait datastructures at a high rate. Unfortunately the current latch interface makes it hard to allocate any persistent per-backend resources. Replace, with a backward compatibility layer, WaitLatchOrSocket with a new WaitEventSet API. Users can allocate such a Set across multiple calls, and add more than one file-descriptor to wait on. The latter has been added because there's upcoming postgres features where that will be helpful. In addition to the previously existing poll(2), select(2), WaitForMultipleObjects() implementations also provide an epoll_wait(2) based implementation to address the aforementioned performance problem. Epoll is only available on linux, but that is the most likely OS for machines large enough (four sockets) to reproduce the problem. To actually address the aforementioned regression, create and use a long-lived WaitEventSet for FE/BE communication. There are additional places that would benefit from a long-lived set, but that's a task for another day. Thanks to Amit Kapila, who helped make the windows code I blindly wrote actually work. Reported-By: Dmitry Vasilyev Discussion: CAB-SwXZh44_2ybvS5Z67p_CDz=XFn4hNAD=CnMEF+QqkXwFrGg@mail.gmail.com 20160114143931.GG10941@awork2.anarazel.de
2016-03-19Remove dependency on psed for MSVC builds.Andrew Dunstan
Modern Perl has removed psed from its core distribution, so it might not be readily available on some build platforms. We therefore replace its use with a Perl script generated by s2p, which is equivalent to the sed script. The latter is retained for non-MSVC builds to avoid creating a new hard dependency on Perl for non-Windows tarball builds. Backpatch to all live branches. Michael Paquier and me.
2016-03-18Merge wal_level "archive" and "hot_standby" into new name "replica"Peter Eisentraut
The distinction between "archive" and "hot_standby" existed only because at the time "hot_standby" was added, there was some uncertainty about stability. This is now a long time ago. We would like to move forward with simplifying the replication configuration, but this distinction is in the way, because a primary server cannot tell (without asking a standby or predicting the future) which one of these would be the appropriate level. Pick a new name for the combined setting to make it clearer that it covers all (non-logical) backup and replication uses. The old values are still accepted but are converted internally. Reviewed-by: Michael Paquier <michael.paquier@gmail.com> Reviewed-by: David Steele <david@pgmasters.net>
2016-03-18Use INT64_FORMAT instead of %ld for int64.Robert Haas
Commit 0011c0091e886b874e485a46ff2c94222ffbf550 introduced this mistake. Patch by me. Reported by Andres Freund, who also reviewed the patch.
2016-03-18Introduce parse_ident()Teodor Sigaev
SQL-layer function to split qualified identifier into array parts. Author: Pavel Stehule with minor editorization by me and Jim Nasby
2016-03-18Various minor corrections of and improvements to comments.Robert Haas
Aleksander Alekseev
2016-03-17Update tuplesort.c comments for memory mangement improvements.Robert Haas
I'm committing these changes separately so that it's clear what is Peter's original work versus what I changed. This is a followup to commit 0011c0091e886b874e485a46ff2c94222ffbf550, and these changes are all by me.
2016-03-17Improve memory management for external sorts.Robert Haas
Introduce a new memory context which stores tuple data, and reset it at the end of each merge pass; this helps avoid memory fragmentation and, consequently, overallocation. Also, for the final merge patch, eliminate memory context chunk header overhead entirely by allocating all of the memory used for buffering tuples during the merge in a single chunk. Since this modestly increases the number of tuples we can store, grow the memtuples array a bit so that we're less likely to run short of slots there. Peter Geoghegan. Review and testing of patches in this series by Jeff Janes, Greg Stark, Mithun Cy, and me.
2016-03-17Fix assorted breakage in to_char()'s OF format option.Tom Lane
In HEAD, fix incorrect field width for hours part of OF when tm_gmtoff is negative. This was introduced by commit 2d87eedc1d4468d3 as a result of falsely applying a pattern that's correct when + signs are omitted, which is not the case for OF. In 9.4, fix missing abs() call that allowed a sign to be attached to the minutes part of OF. This was fixed in 9.5 by 9b43d73b3f9bef27, but for inscrutable reasons not back-patched. In all three versions, ensure that the sign of tm_gmtoff is correctly reported even when the GMT offset is less than 1 hour. Add regression tests, which evidently we desperately need here. Thomas Munro and Tom Lane, per report from David Fetter
2016-03-16Add syslog_split_messages parameterPeter Eisentraut
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
2016-03-16Add syslog_sequence_numbers parameterPeter Eisentraut
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
2016-03-16Fix j2day() to behave sanely for negative Julian dates.Tom Lane
Somebody had apparently once figured that casting to unsigned int would produce the right output for negative inputs, but that would only be true if 2^32 were a multiple of 7, which of course it ain't. We need to use a signed division and then correct the sign of the remainder. AFAICT, the only case where this would arise currently is when doing ISO-week calculations for dates in 4714BC, where we'd compute a negative Julian date representing 4714-01-04BC and then do some arithmetic with it. Since we don't even really document support for such dates, this is not of much consequence. But we may as well get it right. Per report from Vitaly Burovoy.
2016-03-16Be more careful about out-of-range dates and timestamps.Tom Lane
Tighten the semantics of boundary-case timestamptz so that we allow timestamps >= '4714-11-24 00:00+00 BC' and < 'ENDYEAR-01-01 00:00+00 AD' exactly, no more and no less, but it is allowed to enter timestamps within that range using non-GMT timezone offsets (which could make the nominal date 4714-11-23 BC or ENDYEAR-01-01 AD). This eliminates dump/reload failure conditions for timestamps near the endpoints. To do this, separate checking of the inputs for date2j() from the final range check, and allow the Julian date code to handle a range slightly wider than the nominal range of the datatypes. Also add a bunch of checks to detect out-of-range dates and timestamps that formerly could be returned by operations such as date-plus-integer. All C-level functions that return date, timestamp, or timestamptz should now be proof against returning a value that doesn't pass IS_VALID_DATE() or IS_VALID_TIMESTAMP(). Vitaly Burovoy, reviewed by Anastasia Lubennikova, and substantially whacked around by me
2016-03-16Add idle_in_transaction_session_timeout.Robert Haas
Vik Fearing, reviewed by Stéphane Schildknecht and me, and revised slightly by me.
2016-03-16UCS_to_EUC_JIS_2004.pl: Turn off "test" mode by defaultPeter Eisentraut
It produces debugging output files that are of no further use, so we don't need that by default.
2016-03-16Make spacing and punctuation consistentPeter Eisentraut
2016-03-15Fix typos.Robert Haas
Oskari Saarenmaa
2016-03-13Report memory context stats upon out-of-memory in repalloc[_huge].Tom Lane
This longstanding functionality evidently got lost in commit 3d6d1b585524aab6. Noted while studying an OOM report from Jaime Casanova. Backpatch to 9.5 where the bug was introduced.
2016-03-12Fix Windows portability issue in 23a27b039d94ba35.Tom Lane
_strtoui64() is available in MSVC builds, but apparently not with other Windows toolchains. Thanks to Petr Jelinek for the diagnosis.
2016-03-12Widen query numbers-of-tuples-processed counters to uint64.Tom Lane
This patch widens SPI_processed, EState's es_processed field, PortalData's portalPos field, FuncCallContext's call_cntr and max_calls fields, ExecutorRun's count argument, PortalRunFetch's result, and the max number of rows in a SPITupleTable to uint64, and deals with (I hope) all the ensuing fallout. Some of these values were declared uint32 before, and others "long". I also removed PortalData's posOverflow field, since that logic seems pretty useless given that portalPos is now always 64 bits. The user-visible results are that command tags for SELECT etc will correctly report tuple counts larger than 4G, as will plpgsql's GET GET DIAGNOSTICS ... ROW_COUNT command. Queries processing more tuples than that are still not exactly the norm, but they're becoming more common. Most values associated with FETCH/MOVE distances, such as PortalRun's count argument and the count argument of most SPI functions that have one, remain declared as "long". It's not clear whether it would be worth promoting those to int64; but it would definitely be a large dollop of additional API churn on top of this, and it would only help 32-bit platforms which seem relatively less likely to see any benefit. Andreas Scherbaum, reviewed by Christian Ullrich, additional hacking by me
2016-03-11Fix Windows build broken in 6943a946c7e5eb72d53c0ce71f08a81a133503bdTeodor Sigaev
Also it fixes dynamic array allocation disallowed by ANSI-C. Author: Stas Kelvich
2016-03-11Tsvector editing functionsTeodor Sigaev
Adds several tsvector editting function: convert tsvector to/from text array, set weight for given lexemes, delete lexeme(s), unnest, filter lexemes with given weights Author: Stas Kelvich with some editorization by me Reviewers: Tomas Vondram, Teodor Sigaev
2016-03-11Allow emit_log_hook to see original message textSimon Riggs
emit_log_hook could only see the translated text, making it harder to identify which message was being sent. Pass original text to allow the exact message to be identified, whichever language is used for logging. Discussion: 20160216.184755.59721141.horiguchi.kyotaro@lab.ntt.co.jp Author: Kyotaro Horiguchi
2016-03-10Allow to trigger kernel writeback after a configurable number of writes.Andres Freund
Currently writes to the main data files of postgres all go through the OS page cache. This means that some operating systems can end up collecting a large number of dirty buffers in their respective page caches. When these dirty buffers are flushed to storage rapidly, be it because of fsync(), timeouts, or dirty ratios, latency for other reads and writes can increase massively. This is the primary reason for regular massive stalls observed in real world scenarios and artificial benchmarks; on rotating disks stalls on the order of hundreds of seconds have been observed. On linux it is possible to control this by reducing the global dirty limits significantly, reducing the above problem. But global configuration is rather problematic because it'll affect other applications; also PostgreSQL itself doesn't always generally want this behavior, e.g. for temporary files it's undesirable. Several operating systems allow some control over the kernel page cache. Linux has sync_file_range(2), several posix systems have msync(2) and posix_fadvise(2). sync_file_range(2) is preferable because it requires no special setup, whereas msync() requires the to-be-flushed range to be mmap'ed. For the purpose of flushing dirty data posix_fadvise(2) is the worst alternative, as flushing dirty data is just a side-effect of POSIX_FADV_DONTNEED, which also removes the pages from the page cache. Thus the feature is enabled by default only on linux, but can be enabled on all systems that have any of the above APIs. While desirable and likely possible this patch does not contain an implementation for windows. With the infrastructure added, writes made via checkpointer, bgwriter and normal user backends can be flushed after a configurable number of writes. Each of these sources of writes controlled by a separate GUC, checkpointer_flush_after, bgwriter_flush_after and backend_flush_after respectively; they're separate because the number of flushes that are good are separate, and because the performance considerations of controlled flushing for each of these are different. A later patch will add checkpoint sorting - after that flushes from the ckeckpoint will almost always be desirable. Bgwriter flushes are most of the time going to be random, which are slow on lots of storage hardware. Flushing in backends works well if the storage and bgwriter can keep up, but if not it can have negative consequences. This patch is likely to have negative performance consequences without checkpoint sorting, but unfortunately so has sorting without flush control. Discussion: alpine.DEB.2.10.1506011320000.28433@sto Author: Fabien Coelho and Andres Freund